For the connection of flexible tubes to fixed devices, such as valves, joint elements, reducers, user equipment and the like, connections of various types are used; generally it is required that such connectors assure both the hydraulic or pneumatic seal and also the mechanical locking of the tubes.
A fundamental requirement, especially for installations in the case of the construction of large dimensions, such as for example industrial or domestic hydraulic distribution systems, is that the connections can be made especially rapidly without, however, detracting from the firmness and stability of the connection.
In many cases, moreover, the flexible tubes or pipes used are subject to dimensional variations, for example as a consequence of temperature fluctuations during operation, as in the case of heating or hot water distribution installations, or due to a drop in the ambient temperature; in such cases, as a result of an expansion, it is possible for the tube to depart from the path assigned to it. Compression forces may act upon the end connections of the tube and results in contraction. In the case where a departure from the path of the tube in a layout of short length is prevented, for example in the case of an initial straight layout, tensile forces act upon the end connections, which may also lead to disengagement of one end of the tube from the connection.